With the arrival of pollinator wasp, bo tree can reproduce

Ki‘ai Moku

October 13, 2013

Lori Buchanan, manager of Molokai/Maui Invasive Species Committee, was in downtown Kaunakakai recently when she saw something strange sprouting out of the storm drain. It was a 3-foot-tall seedling of a ficus - the very same tree she and her crew are working to remove from Molokai.

Called the bo, peepul or bodhi tree, Ficus religiosa is planted throughout Asia, Africa and North America. According to legend, the Buddha sat beneath this species of tree when he meditated and attained enlightenment, hence its name. The Hindu deity Vishnu is reputed to have been born under a bo tree. These trees are often planted at Buddhist and Hindu temples. There is a bo tree at the Foster Botanical Garden on Oahu that is said to be a descendant of the tree under which Buddha sat.

Not that long ago, the bo tree couldn't reproduce on its own in Hawaii; it only grew via cuttings. As a member of the Ficus family, it needs a specific wasp to pollinate its flowers in order to produce seeds. That wasp, Blastophaga quadraticeps, was not in Hawaii. The wasp crawls inside the minute flower to fertilize it. In 2007, when seedlings sprang up under the bo tree at Foster Garden, Hawaii entomologists knew the pollinator wasp had arrived.

Article Photos

This seedling was found sprouting out of a sidewalk in downtown Kaunakakai. The Molokai/Maui Invasive Species Committee is working to protect Molokai’s native forest from the bo tree.

FOREST and KIM STARR photo

The arrival of Blastophaga quadraticeps means that Hawaii has joined a relatively small list of places where Ficus religiosa can produce viable seed: India (where it's native), Israel and Florida. In Israel, the pollinator wasp fully invaded and Ficus religiosa now ranks alongside other Ficus as invasive and messy. Now that they produce fruit in Israel, purple figs stain the sidewalks, stick to shoes, and splatter cars left in the shade of a tree. Motorcyclists dodge slippery piles of fruit and beachgoers clean gummy residue off their gear.

On Molokai, Buchanan isn't worried about sidewalk saplings - she's worried about the forests. "Birds spread the seeds, and they (Ficus trees) can get into the forest and threaten the watershed," she says. "They are prolific seeders and seedlings pop up wherever." The Bo tree could start to take over the native forest on Molokai.

Ficus religiosa, like most Ficus, can grow almost epiphytically: a seedling doesn't need soil initially but roots reach down until they find earth. The bo tree is technically more of a "splitter" than a strangler fig. Rather than smothering its host in roots, the seeds that sprout in the fork of a tree will send roots through the stem of the support tree, splitting it from the inside. It can find a home in sidewalks and drain sprouts, splitting those apart as well.

The Invasive Species Committee is actively controlling this species on Molokai, where fewer than a dozen trees were planted. Only one mature tree remains, and Buchanan and her crew are busy hunting down seedlings until the landowner agrees to have the plant removed. On other islands the bo tree is planted widely enough that resources are too limited to remove it. But choosing to not plant this tree will slow its spread.

You can help by keeping an eye out for bo tree seedlings in Central Molokai, specifically in Kalae and Kaunakakai. The bo tree has distinctive heart-shaped leaves that extend at the tip. According to Buchanan, the plant most closely resembles the Polynesian "canoe plant" milo, which also grows in the same areas on Molokai. The bo tree has more dark green-to-gray glossy leaves. Any sightings of bo tree on Molokai should be reported by calling 954-6585.

* Lissa Fox Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia'i Moku, "Guarding the Island," is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island's environment, economy and quality of life.